<template>
    <!-- 菜单栏 -->
  <div class="Design">
   <div class="Design-a">A</div>
  <div class="Design-b">B</div>
  <div class="Design-c">C</div>
 </div>
    </template>
    <script>
    </script>
    <style>
    
    .Design{
 display: flex;
    }
    .Design-a,.Design-c{
    flex-basis: 100px;
    border: 1px solid #ccc;
    height: 100vh;
    width: 300px;
        }
    .Design-b{
    flex-grow:1;
    border: 1px solid hsl(123, 71%, 44%);
    width: 300px;
        }
        </style>